The invention described herein relates generally to particle separation and classification, and more particularly to methods and apparatus for separating or classifying ensembles of particles of assorted size into their various size fractions.
There are a number of known methods whereby particle classification is presently accomplished. In one such method particulate material is allowed to fall, under the influence of gravity, through a generally horizontal air flow, with the differential displacement of the material in the air flow direction, which is functional of particle mass, size and shape, being the factor determinative of classification. In another known method cyclone separators, wherein centrifugal force is generated by the tangential introduction of a high-velocity fluid stream into a conically cylindrical chamber, are used to remove liquid drops or solid particles from gases.
However, if one is confronted with the task of classifying into size fractions, tens or hundreds of grams of a typical powder, made up of often irregularly shaped particles ranging in size from tenths to hundreds of microns in diameter, one immediately perceives that the presently known methods of particle separation and classification are slow, tedious, inefficient and generally inadequate.